Task 333: .JS File Format

The .JS file format refers to JavaScript source code files. These are plain text files containing JavaScript code that conforms to the ECMAScript Language Specification (ECMA-262). There is no binary structure, magic number, or fixed header; the content is human-readable text, typically encoded in UTF-8 or ASCII.

Since the .JS file format has no format-specific binary or structural properties (it's plain text), the properties intrinsic to its file system are the standard metadata attributes associated with any regular file. These can vary slightly by operating system and file system, but common ones include:

• File name
• File path
• Size (in bytes)
• Creation time
• Last modification time
• Last access time
• Permissions (e.g., read/write/execute bits for owner, group, and others, often represented in octal)
• Owner user ID (or name)
• Owner group ID (or name)
• Inode number (on Unix-like systems)
• Number of hard links
• Device ID
• File type (regular file)

Two direct download links for .JS files:

• https://code.jquery.com/jquery-3.7.1.js
• https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.js

Below is an embeddable HTML snippet with JavaScript (suitable for a Ghost blog post or similar CMS via raw HTML embedding) that sets up a drag-and-drop zone. It dumps the available properties to the screen for a dropped .JS file. Note: Browser security limits access to full file system metadata; only basic File API properties are available (e.g., no permissions, owner, or creation time beyond last modified).

1. Below is a Python class. It opens a .JS file (reading it as text since there's no binary decoding needed), retrieves the file system properties via os.stat, provides methods to read/write the file content (for completeness, as .JS is text-based), and prints the properties to console. Usage example: handler = JSFileHandler('example.js'); handler.print_properties().

import os
import time

class JSFileHandler:
    def __init__(self, filename):
        if not filename.lower().endswith('.js'):
            raise ValueError("File must have .js extension")
        self.filename = filename
        self.stat = os.stat(filename)

    def decode_read_content(self):
        # No binary decoding needed; read as text
        with open(self.filename, 'r', encoding='utf-8') as f:
            return f.read()

    def write_content(self, content):
        with open(self.filename, 'w', encoding='utf-8') as f:
            f.write(content)

    def print_properties(self):
        print(f"File name: {os.path.basename(self.filename)}")
        print(f"File path: {os.path.abspath(self.filename)}")
        print(f"Size (in bytes): {self.stat.st_size}")
        print(f"Creation time: {time.ctime(self.stat.st_ctime)}")
        print(f"Last modification time: {time.ctime(self.stat.st_mtime)}")
        print(f"Last access time: {time.ctime(self.stat.st_atime)}")
        print(f"Permissions: {oct(self.stat.st_mode)}")
        print(f"Owner user ID (or name): {self.stat.st_uid}")
        print(f"Owner group ID (or name): {self.stat.st_gid}")
        print(f"Inode number: {self.stat.st_ino}")
        print(f"Number of hard links: {self.stat.st_nlink}")
        print(f"Device ID: {self.stat.st_dev}")
        print(f"File type: regular file")

1. Below is a Java class. It opens a .JS file (reading it as text since there's no binary decoding needed), retrieves the file system properties via java.nio.file, provides methods to read/write the file content, and prints the properties to console. Requires Java 8+. Usage example: JSFileHandler handler = new JSFileHandler("example.js"); handler.printProperties();.

import java.io.*;
import java.nio.file.*;
import java.nio.file.attribute.*;
import java.time.Instant;

public class JSFileHandler {
    private final Path path;
    private final BasicFileAttributes attrs;

    public JSFileHandler(String filename) throws IOException {
        if (!filename.toLowerCase().endsWith(".js")) {
            throw new IllegalArgumentException("File must have .js extension");
        }
        this.path = Paths.get(filename);
        this.attrs = Files.readAttributes(path, BasicFileAttributes.class);
    }

    public String decodeReadContent() throws IOException {
        // No binary decoding needed; read as text
        return Files.readString(path);
    }

    public void writeContent(String content) throws IOException {
        Files.writeString(path, content);
    }

    public void printProperties() {
        PosixFileAttributes posixAttrs = null;
        try {
            posixAttrs = Files.readAttributes(path, PosixFileAttributes.class);
        } catch (UnsupportedOperationException | IOException e) {
            // Fallback for non-Posix systems (e.g., Windows)
        }
        System.out.println("File name: " + path.getFileName());
        System.out.println("File path: " + path.toAbsolutePath());
        System.out.println("Size (in bytes): " + attrs.size());
        System.out.println("Creation time: " + Instant.ofEpochMilli(attrs.creationTime().toMillis()));
        System.out.println("Last modification time: " + Instant.ofEpochMilli(attrs.lastModifiedTime().toMillis()));
        System.out.println("Last access time: " + Instant.ofEpochMilli(attrs.lastAccessTime().toMillis()));
        if (posixAttrs != null) {
            System.out.println("Permissions: " + posixAttrs.permissions());
            System.out.println("Owner user ID (or name): " + posixAttrs.owner().getName());
            System.out.println("Owner group ID (or name): " + posixAttrs.group().getName());
        } else {
            System.out.println("Permissions: (Not available on this system)");
            System.out.println("Owner user ID (or name): " + attrs.owner());
            System.out.println("Owner group ID (or name): (Not available on this system)");
        }
        System.out.println("Inode number: (Not directly available in Java)");
        System.out.println("Number of hard links: (Not directly available in Java)");
        System.out.println("Device ID: (Not directly available in Java)");
        System.out.println("File type: " + (attrs.isRegularFile() ? "regular file" : "other"));
    }
}

1. Below is a JavaScript class (for Node.js environment). It opens a .JS file (reading it as text since there's no binary decoding needed), retrieves the file system properties via fs.statSync, provides methods to read/write the file content, and prints the properties to console. Usage example: const handler = new JSFileHandler('example.js'); handler.printProperties();.

const fs = require('fs');
const path = require('path');

class JSFileHandler {
  constructor(filename) {
    if (!filename.toLowerCase().endsWith('.js')) {
      throw new Error('File must have .js extension');
    }
    this.filename = filename;
    this.stat = fs.statSync(filename);
  }

  decodeReadContent() {
    // No binary decoding needed; read as text
    return fs.readFileSync(this.filename, 'utf-8');
  }

  writeContent(content) {
    fs.writeFileSync(this.filename, content, 'utf-8');
  }

  printProperties() {
    console.log(`File name: ${path.basename(this.filename)}`);
    console.log(`File path: ${path.resolve(this.filename)}`);
    console.log(`Size (in bytes): ${this.stat.size}`);
    console.log(`Creation time: ${this.stat.birthtime}`);
    console.log(`Last modification time: ${this.stat.mtime}`);
    console.log(`Last access time: ${this.stat.atime}`);
    console.log(`Permissions: ${this.stat.mode.toString(8)}`);
    console.log(`Owner user ID (or name): ${this.stat.uid}`);
    console.log(`Owner group ID (or name): ${this.stat.gid}`);
    console.log(`Inode number: ${this.stat.ino}`);
    console.log(`Number of hard links: ${this.stat.nlink}`);
    console.log(`Device ID: ${this.stat.dev}`);
    console.log(`File type: regular file`);
  }
}

1. Below is a C++ class (since standard C has no classes; assuming C++ for object-oriented support). It opens a .JS file (reading it as text since there's no binary decoding needed), retrieves the file system properties via stat, provides methods to read/write the file content, and prints the properties to console. Compile with g++ and run. Usage example: JSFileHandler handler("example.js"); handler.print_properties();. Note: This uses Unix-like stat; on Windows, use _stat or equivalent.

#include <iostream>
#include <fstream>
#include <string>
#include <sys/stat.h>
#include <ctime>
#include <unistd.h>  // For getuid, etc., if needed

class JSFileHandler {
private:
    std::string filename;
    struct stat file_stat;

public:
    JSFileHandler(const std::string& fname) : filename(fname) {
        if (filename.length() < 3 || filename.substr(filename.length() - 3) != ".js") {
            throw std::invalid_argument("File must have .js extension");
        }
        if (::stat(filename.c_str(), &file_stat) != 0) {
            throw std::runtime_error("Failed to get file stats");
        }
    }

    std::string decode_read_content() {
        // No binary decoding needed; read as text
        std::ifstream file(filename);
        if (!file) {
            throw std::runtime_error("Failed to open file for reading");
        }
        std::string content((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
        return content;
    }

    void write_content(const std::string& content) {
        std::ofstream file(filename);
        if (!file) {
            throw std::runtime_error("Failed to open file for writing");
        }
        file << content;
    }

    void print_properties() {
        std::cout << "File name: " << filename << std::endl;  // basename not used for simplicity
        std::cout << "File path: " << std::string(std::filesystem::absolute(filename)) << std::endl;  // Requires C++17
        std::cout << "Size (in bytes): " << file_stat.st_size << std::endl;
        std::cout << "Creation time: " << std::ctime(&file_stat.st_ctime);
        std::cout << "Last modification time: " << std::ctime(&file_stat.st_mtime);
        std::cout << "Last access time: " << std::ctime(&file_stat.st_atime);
        std::cout << "Permissions: " << std::oct << file_stat.st_mode << std::dec << std::endl;
        std::cout << "Owner user ID (or name): " << file_stat.st_uid << std::endl;
        std::cout << "Owner group ID (or name): " << file_stat.st_gid << std::endl;
        std::cout << "Inode number: " << file_stat.st_ino << std::endl;
        std::cout << "Number of hard links: " << file_stat.st_nlink << std::endl;
        std::cout << "Device ID: " << file_stat.st_dev << std::endl;
        std::cout << "File type: regular file" << std::endl;
    }
};